The major goal of this preclinical IPCP project is the development of lentiviral vectors for gene therapy of HIV-based vectors that target hematopoietic cells, including stem cells and dendritic cells for antiviral and immune-based therapies. Our specific aims are: 1. To establish optimal HIV-2 gene transfer vector and stable packaging lines-Efforts will be made to minimize the chance of PCR generation, while optimizing vector titers. 2. To demonstrate protection of primary T cells, macrophages and progeny of CD34+ cells by lentiviral vector transduction against HIV challenge-HIV-2 vectors expressing anti-HIV-1 and anti-CCR5 ribozymes will be tested in these studies. We will also ascertain whether transduction by these vectors will have any deleterious effect on cell proliferation, differentiation and/or function of these target cells. 3. To examine the effect of lentiviral vector transduction on dendritic cell function and interaction with T cells-Dendritic cells (DC) are both facilitators and defenders of HIV infection since they can present both viral antigens and infectious virus to T cells. Recent data suggest that while only immature DC's are infectiable by HIV, mature DC's need to express functional chemokine receptors CCR5 and CXC4 to transmit M-tropic and T-tropic and T-tropic viruses to CD4+ T cells respectively. We will construct HIV- 1 vectors expressing gag-pol antigens as well as anti-CCR-5 and/or anti CXCR4 ribozymes, and determine how transduction by these vectors will impact on the ability of dendritic cells to be present antigen to CD4 and CD8 cells or to transmit HIV infection to CD4 cells. In addition to these aims, this project will collaborate closely with Projects 2 and 3 to directly compare the safety and efficacy of HIV-based and FIV-based lentiviral vectors and MLV-based retroviral vectors in vitro and in vivo.